One can say that The very nature of Impedance and Resistance is same.
Which resist the flow of current is known as Resistance. And is represented by R.
Now in AC circuits besides Resistance, it has Capacitance and Inductance. And this Capacitance, Resistance and Inductance together form Impedance which is denoted by Z.
One can say the Impedance for DC circuit is its Resistance
Edit : (copied from comment)
Well Impedance of any circuit (DC or AC) is comination of R,LC (Resistance, Inidcutance, Capacitance). We can say Total Impedance Z = ZR+ZL+ZC
Now impedance of inductors increases as frequency increases
ZL = jwL
and, impedance of capacitors decreases as frequency increases
now both Zl and ZC is frequency dependent component.
So for AC circuit Z=ZR+ZL+ZC
and in DC cicrcuit, we don't have any frequency,
so it becomes Z=ZR
In DC circuit Resistance is the Impedance (due to no existance of capacitance and inductance)